Conventionally, in radar apparatuses, there has been a problem in which, a display quality of a radar image may be degraded when electromagnetic waves (interference component) transmitted from other ships are contained in an echo signal.
Thus, another radar apparatus is proposed, which determines as interference when only a signal corresponding to one sweep before the current sweep among three or more consecutive signals of the same azimuth and distance exceeds a threshold, and removes the interference by not displaying the signal (zero substitution) (see JP H05-027011(A)).
However, low level interferences may occur in fact, and if raising the threshold and weakening the interference removing processing, there has been a problem in which the interferences cannot be removed sufficiently. On the other hand, if lowering the threshold, the echo signals from target objects which are necessary may be removed.